[llvm-branch-commits] [llvm] b4429f3 - [SimplifyCFG] Teach removeUndefIntroducingPredecessor to preserve DomTree

[Roman Lebedev via llvm-branch-commits]

Author: Roman Lebedev
Date: 2021-01-02T01:01:20+03:00
New Revision: b4429f3cdd1a8511bd014877b22d9679c4a74dbd

URL: https://github.com/llvm/llvm-project/commit/b4429f3cdd1a8511bd014877b22d9679c4a74dbd
DIFF: https://github.com/llvm/llvm-project/commit/b4429f3cdd1a8511bd014877b22d9679c4a74dbd.diff

LOG: [SimplifyCFG] Teach removeUndefIntroducingPredecessor to preserve DomTree

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/test/CodeGen/Hexagon/misaligned_double_vector_store_not_fast.ll
    llvm/test/CodeGen/Hexagon/swp-epilog-phi10.ll
    llvm/test/CodeGen/Hexagon/swp-order-deps3.ll
    llvm/test/CodeGen/Hexagon/swp-reuse-phi-4.ll
    llvm/test/CodeGen/Thumb2/2009-08-04-CoalescerBug.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 37e594dbd1a4..fa12d8b99644 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6563,14 +6563,16 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) {
 
 /// If BB has an incoming value that will always trigger undefined behavior
 /// (eg. null pointer dereference), remove the branch leading here.
-static bool removeUndefIntroducingPredecessor(BasicBlock *BB) {
+static bool removeUndefIntroducingPredecessor(BasicBlock *BB,
+                                              DomTreeUpdater *DTU) {
   for (PHINode &PHI : BB->phis())
     for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i)
       if (passingValueIsAlwaysUndefined(PHI.getIncomingValue(i), &PHI)) {
-        Instruction *T = PHI.getIncomingBlock(i)->getTerminator();
+        BasicBlock *Predecessor = PHI.getIncomingBlock(i);
+        Instruction *T = Predecessor->getTerminator();
         IRBuilder<> Builder(T);
         if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
-          BB->removePredecessor(PHI.getIncomingBlock(i));
+          BB->removePredecessor(Predecessor);
           // Turn uncoditional branches into unreachables and remove the dead
           // destination from conditional branches.
           if (BI->isUnconditional())
@@ -6579,6 +6581,9 @@ static bool removeUndefIntroducingPredecessor(BasicBlock *BB) {
             Builder.CreateBr(BI->getSuccessor(0) == BB ? BI->getSuccessor(1)
                                                        : BI->getSuccessor(0));
           BI->eraseFromParent();
+          if (DTU)
+            DTU->applyUpdatesPermissive(
+                {{DominatorTree::Delete, Predecessor, BB}});
           return true;
         }
         // TODO: SwitchInst.
@@ -6611,7 +6616,7 @@ bool SimplifyCFGOpt::simplifyOnceImpl(BasicBlock *BB) {
   Changed |= EliminateDuplicatePHINodes(BB);
 
   // Check for and remove branches that will always cause undefined behavior.
-  Changed |= removeUndefIntroducingPredecessor(BB);
+  Changed |= removeUndefIntroducingPredecessor(BB, DTU);
 
   // Merge basic blocks into their predecessor if there is only one distinct
   // pred, and if there is only one distinct successor of the predecessor, and

diff  --git a/llvm/test/CodeGen/Hexagon/misaligned_double_vector_store_not_fast.ll b/llvm/test/CodeGen/Hexagon/misaligned_double_vector_store_not_fast.ll
index ba867e68a95e..0945e17531be 100644
--- a/llvm/test/CodeGen/Hexagon/misaligned_double_vector_store_not_fast.ll
+++ b/llvm/test/CodeGen/Hexagon/misaligned_double_vector_store_not_fast.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=hexagon -O3 -debug-only=isel 2>&1 -simplifycfg-require-and-preserve-domtree=0 < %s | FileCheck %s
+; RUN: llc -march=hexagon -O3 -debug-only=isel 2>&1 -simplifycfg-require-and-preserve-domtree=1 < %s | FileCheck %s
 ; REQUIRES: asserts
 
 ; DAGCombiner converts the two vector stores to a double vector store,

diff  --git a/llvm/test/CodeGen/Hexagon/swp-epilog-phi10.ll b/llvm/test/CodeGen/Hexagon/swp-epilog-phi10.ll
index 192f1356fe42..5b5b45d13210 100644
--- a/llvm/test/CodeGen/Hexagon/swp-epilog-phi10.ll
+++ b/llvm/test/CodeGen/Hexagon/swp-epilog-phi10.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=hexagon -mcpu=hexagonv5 -simplifycfg-require-and-preserve-domtree=0 < %s
+; RUN: llc -march=hexagon -mcpu=hexagonv5 -simplifycfg-require-and-preserve-domtree=1 < %s
 ; REQUIRES: asserts
 
 define void @test(i8* noalias nocapture readonly %src, i32 %srcStride) local_unnamed_addr #0 {

diff  --git a/llvm/test/CodeGen/Hexagon/swp-order-deps3.ll b/llvm/test/CodeGen/Hexagon/swp-order-deps3.ll
index 6f5245348187..e85d35549385 100644
--- a/llvm/test/CodeGen/Hexagon/swp-order-deps3.ll
+++ b/llvm/test/CodeGen/Hexagon/swp-order-deps3.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=hexagon -O2 -simplifycfg-require-and-preserve-domtree=0 < %s
+; RUN: llc -march=hexagon -O2 -simplifycfg-require-and-preserve-domtree=1 < %s
 ; REQUIRES: asserts
 
 ; Function Attrs: noinline nounwind ssp

diff  --git a/llvm/test/CodeGen/Hexagon/swp-reuse-phi-4.ll b/llvm/test/CodeGen/Hexagon/swp-reuse-phi-4.ll
index 197e02cfceb4..4a309d5e31e1 100644
--- a/llvm/test/CodeGen/Hexagon/swp-reuse-phi-4.ll
+++ b/llvm/test/CodeGen/Hexagon/swp-reuse-phi-4.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=hexagon -O2 -simplifycfg-require-and-preserve-domtree=0 < %s
+; RUN: llc -march=hexagon -O2 -simplifycfg-require-and-preserve-domtree=1 < %s
 ; REQUIRES: asserts
 
 ; Test that we generate the correct Phi names in the epilog when we need

diff  --git a/llvm/test/CodeGen/Thumb2/2009-08-04-CoalescerBug.ll b/llvm/test/CodeGen/Thumb2/2009-08-04-CoalescerBug.ll
index 93fcf745469d..20da9ba595b7 100644
--- a/llvm/test/CodeGen/Thumb2/2009-08-04-CoalescerBug.ll
+++ b/llvm/test/CodeGen/Thumb2/2009-08-04-CoalescerBug.ll
@@ -1,4 +1,4 @@
-; RUN: llc -simplifycfg-require-and-preserve-domtree=0 < %s -mtriple=thumbv7-apple-darwin -mcpu=cortex-a8 -relocation-model=pic -frame-pointer=all
+; RUN: llc -simplifycfg-require-and-preserve-domtree=1 < %s -mtriple=thumbv7-apple-darwin -mcpu=cortex-a8 -relocation-model=pic -frame-pointer=all
 
 	%0 = type { %struct.GAP }		; type %0
 	%1 = type { i16, i8, i8 }		; type %1